Meat. For generations, it has been center stage on American dinner plates, but now, for many, its seems to be moving to the side of the plate.

Today, 30 percent of Americans are eating less meat, not necessarily going vegetarian or vegan, but choosing to eat less. Concerns over health, the so-called "pink slime" in burgers controversy, the impact on the environment and higher prices at the grocery store have led to meal-overhaul movements such as "Meatless Mondays" and a 12-percent drop in meat consumption over the last five years.

While finding new ways to change your diet can seem like a challenge, Mark Bittman, a New York Times food critic and an advocate for "less-meatarians," is out to prove that anyone can easily and affordably make tasty meals without having a chunk of meat take over the dinner plate.

"Combining vegetables with meat makes them much more interesting and this is historically how people ate," Bittman said. "Meat and fish were treasures. They were treats. They were things you couldn't count on. It's only in the past 50 years that you could count on putting meat on the table every night and every day."

"The difference isn't really between an organic cheese burger and a non-organic cheeseburger," he said. "The difference is between ... a cheeseburger and a head of broccoli. That's the real choice."

At Haven's Kitchen in New York City, Bittman cooked up a cassoulet, basically pork and beans, but light on the pork. He said it's a healthier meal because it is lower in fat and higher in micronutrients than its more traditional cousin. Bittman said eating less meat has helped improve his health.

"I lost 35 pounds, my cholesterol levels went down below 200, which is where it's supposed to be, and blood sugar went down to where it's supposed to be," he said.

To put the "less-meatatarian" diet to the test, "Nightline" asked celebrity chef Angelo Sosa, a committed omnivore who specializes in Asian cuisine, to try it for three days, meaning he had to dial back the meat and amp up the vegetables, fruits and whole grains.

"What I eat is extremely important to me, more so now than ever -- I'm 37 and the weight goes right to my belly," Sosa said. "I'm excited. I feel like I don't need to be weighed down. I don't like more fat in my system."